Panelboard with contact members having orthogonal engageable surfaces



March 14, 1967 K. w. KLEIN 3,309,531

, PANELBOARD WITH CONTACT MEMBERS HAVING ORTHOGONAL ENGAGEABLE SURFACES Filed D60. 24, 1964 2 Sheets-Sheet l I N V EN 1 OR.

KEITH W /(LE/N A TI'ORNEY March 14, 1967 w. KLEIN PANELBOARD WITH CONTACT MEMBERS HAVING ORTHOGONAL ENGAGEABLE SURFACES 2 Sheets-Sheet 2 Filed Dec. 24, 1964 United States Patent PANELBOARD WITH CONTACT MEMBERS HAVING ORTHOGONAL ENGAGEABLE SURFACES Keith W. Klein, Simsbury, Conn., assignor to General Electric Company, a corporation of New York Filed Dec. 24, 1964, Ser. No. 420,875

Claims. (Cl. 317119) This invention relates to circuit breaker panel boards and load centers and especially to such panel boards and load centers which include circuit breakers or fusible means having at least one terminal electrically engageable by a plug-in type connection. 1

Circuit breakers used in such panel boards and load centers are conventionally made in a broad'variety of ampere ratings and different modular s-izes. Cust-omarily related ranges of ampere ratings will be embodied in a common modular size. Usually circuit breakers of the type referred to will be enclosed in insulating casings having generally common dimensions of height and length and varying modularly in width. For instance, the basic module for a common type of smaller circuit breaker may have a nominal one-inch width. Larger modular sizes may have a nominal two-inch width, while the smaller modular size may be a nominal one-half inch width. It has been found from experience in the installa tion of such panel boards and load centers that it is frequently desirable that such panel boards and load cen ters include some means ofsegregating desired portions of the load center so that only circuit breakers of a particular modular size or sizes may be connected into an electrical engagement in such segregated portion.

The present invention is directed to the type of panel board load center and circuit breakers which are engaged in electrical connection by inserting one portion of the circuit breaker in an appropriately configured part of the panel board and rotating the circuit breaker about that point and into plug-in connection with an electrical contact means carried by the panel board. In this type of assembly it is not only desirable to have firm and secure electrical engagement of the contact means, but it is also advantageous to have an arrangement which provides rigid and secure mechanical connection as well, so that the circuit breakers are mechanically supported in their respective desired disposition in mounted engagement upon the panel board load center.

Accordingly, it is a primary object of the present invention to provide an electric circuit breaker panel board including circuit breakers and a load center adaptable to predetermined selective segregation of different modular sizes of circuit breakers.

Another object of the present invention is to provide an electric circuit breaker panel board load center having contact means which, when employed with circuit breakers configurated as conceived by the present invention, insure firm and secure mechanical retention of such circuit breakers in engagement with the contact means of the panel board.

It is a further object of the present invention to provide a control panel board load center of the type described which is not susceptible to the inadvertent or indiscriminate substitution of circuit breakers of one modular size for circuit breakers of another modular size where it is desired that only circuit breakers of the second modular size be employed in a predetermined and selectable portion of the panel board.

In accordance with the concept of the present invention a panel board comprising a generally planar base is provided having insulating means mounted thereon, which insulating means supports a plurality of electrical contacts. The electrical contacts have a particular con- 3,309,581 Patented Mar. 14, 1967 figuration which includes a contact arm portion electrically connected and supported adjacent one end thereof upon a busbar and extending generally normally thereto with a portion adjacent its other or free end spaced above the support having a major transverse dimension and a minor transverse dimension; i.e., a relatively thin section. One or more socket receiving portions project from the contact arm portion adjacent its free end and normally to the plane of the major dimension thereof and parallel to the busbar so that each provides a pair of contact surfaces parallel to the busbar for receiving a contact socket extending transversely of a circuit breaker housing. Generally, for use with the most prevalent commercial breakers, the contact has a central blade having its major transverse dimension extending generally normal to the plane of the base and additionally comprises at least one cylindrically shaped pin extending laterally from the central blade on each side. In the preferred embodiment of the invention, a number of such electrical contacts may be mounted and arranged on the base of the panel board so as to have their central blades substantially parallel to each other and generally aligned centrally on the panel board. Each such central blade may have one or two cylindrically shaped pins extending laterally at right angles on each side; a plurality of circuit break-ers of the first and second modular sizes include appropriate electrical contact means such that the circuit breakers of the first modular size are adapted to engage a central blade and the circuit breakers of the second modular size are adapted to engage one of the cylindrical pins extending laterally at right angles from the central blade of the panel board contacts means.

In accordance with another aspect of the present invention, adjacent electrical contacts of a panel board may be connected to difierent sources of electrical energy. Typically in such an arrangement adjacent electrical con tacts may be arranged to supply two diiferent phases of electrical energy so that the transverse members of such adjacent contacts are disposed to be engageable by two circuit breaker units of the smaller modular size joined in an assembly by appropriate means including a common handle tie to provide a two-pole circuit breaker as sembly.

In a similar manner the present invention is so conceived as to provide three adjacent contacts which are adaptable to connect with three difierent phases of an electrical source. A circuit breaker of the larger modular size and two circuit breakers of the smaller modular size may be joined by appropriate means including a common handle tie to be engageable with an upstanding blade contact and two adjacent transverse contact members on either side as a three pole circuit breaker assembly.

The term circuit breaker as used herein is intended to refer to any device which is capable of making and/or breaking an electric circuit including devices which are manually operable and also those which have fusible means.

The invention will be more fully understood from the following detailed description and its scope will be pointed out in the appended claims.

In the drawings: FIGURE 1 is a top elevational view of a panel boar assembly of the present invention including circuit breakers shown in engagement with the contact means of the panel board;

FIGURE 2 is a cross-sectional view of the panel board of FIGURE 1 taken thnough section 2-2;

FIGURE 3 is a perspective View of a contact means of the panel board of the present invention;

FIGURE 4 is a partially phantom, perspective View of a circuit breaker of the larger modular size;

FIGURE 5 is a partially phantom, perspective view of a circuit breaker of the smaller modular size;

FIGURE 6 is a cross-sectional enlarged view showing the contact means of both the larger modular size circuit breaker and the smaller modular size circuit breaker in engagement with the contact means of the panel board of the present invention;

FIGURE 7 is a partially cross-sectional end view of a two-pole circuit breaker assembly comprising two units of smaller modular size shown in engagement with two adjacent transverse contact members of a panel board;

FIGURE 8 is a three pole circuit breaker assembly comprising one unit of the larger modular size and two units of the smaller modular size shown in engagement with a central blade member and two adjacent transverse contact members of a panel board.

Referring now to FIGURES 1 and 2, there is shown an electrical control panel assembly which comprises a base in the form of a generally channel-shaped supporting pan 10. The pan 10 supports suitable insulating means 11 and 12 which in turn supports bus bars 13 and 14 each having wire connecting means at one end thereof comprising connectors 14A, 15A. Connected to the bus bars 13 and 14 are a plurality of panel board contact units on members as shown generally at 15, 16, 17, 18 and 19. A plurality of circuit breakers 2t 21 and 22 are shown in FIGURE 1 as connected in electrical and mechanical engagement with the panel board assembly. It will be noted that the circuit breakers 20 and 21 are of the smaller modular size, which in this particular illustration may be a nominal one-half inch width, and the circuit breaker 22 is of a larger modular size which may typically have a nominal one-inch width.

The panel board contact member of the present invention has a particular configuration which perhaps may be best seen from the perspective view of FIGURE 3. As illustrated, each of the electrical contact units has a contact arm portion 30 electrically connected and supported adjacent one end thereof upon a busbar 35 (partially shown) and extending generally normally thereto and with its major transverse dimension extending noranally to the support and a minor transverse dimension extending parallel thereto and providing a relatively thin section, such a structure being commonly referred to as a contact blade. Projecting from the contact arm portion 30 adjacent the free end thereof normally to the major dimension thereof and parallel to the busbar 35 are a plurality of socket-receiving portions or pins 31, 32, 33 and 34 which extend in parallel alignment. The pins 31, 32, 33 and 34 are secured by appropriate means to the contact arm portion or central blade 30, such as by welding or by force fit in a recess of appropriate size drilled 0r punched in the contact arm portion or central blade 30, or any combination of such suitable manufacturing techniques. I

As may be seen from FIGURE. 1 the plurality of panel board contact members 15, 16, 17, 18 and 19 are supported upon the bus bars 13 and 14 and arranged so that the central blades of the contact members are aligned centrally on the panel board assembly, generally normal to the base 10 and in parallel relationship with each other. The cylindrical pins extending laterally from the central blades of the contact member 15, 16, 17 and 19 also fall in general alignment over the central portion of the panel board assembly. It will be noted that contact member 18 does not include any laterally extending cylindrical pins and contact member 19 includes only two laterally extending cylindrical pins aligned in opposed relationship on either side of the central blade member. The elimination of one or more of the laterally extending cylindrical pins from the panel board contact members provide means of segregating different modular sizes of circuit breakers in accordance with the concept of the present invention as will be explained more fully hereinafter.

FIGURE 4 illustrates a circuit breaker 36 configured in accordance with the present invention and having contact means or socket shown generally at 37 and comprising opposed resilient jaws 38 and 39 of electrically conductive material. The illustration of FIGURE 4 depicts a circuit breaker of a larger modular size which may typically have a nominal one-inch width and its socket or contact means 37 is aligned with the major axis of the bottom wall of the insulating casing so that it may be inserted intoengagement with the opposite surfaces of the central blade of a panel board contact member as desired.

The manner in which a circuit breaker of the present invention is connected into electrical and mechanical engagement with a panel board assembly of the present invention may be seen by reference to FIGURE 2. The channel-shaped pan, which comprises the main structural member of the base 10', has affixed to either side, flanges 23 and 24 which include an inwardly disposed portion 25 and 26 respectively forming a U-shaped outer section on the flange. A lug means 27 of the insulating casing 28 of the circuit breaker 22 is inserted into the U-shaped section 25 of the flange 23 and the circuit breaker is then rotated about that point of insertion until its contact means or socket 29 comprised of opposed resilient contact jaws comes into electrical and mechanical engagement with the opposite surfaces of a central blade of the panel board contact member. As is best seen in FIGURE 2 the circuit breaker 22 in its fully engaged position is disposed with the inclined or tapered rear portion of its contact jaws abutting the laterally extending cylindrical pins on either side of the central blade member of the contact means and the remaining half of the contact means is left free for engagement by either a circuit breaker of the larger modular size or one or two circuit breakers of the smaller modular size in a manner which will now be explained.

Referring to FIGURE 5, there is shown a phantom outline of a circuit breaker 40 of the smaller modular size which is fitted with a contact means or socket shown generally at 41 and comprised of opposed resilient contact jaws 42 and 43 of electrically conductive material. It will be noted that the contact jaws 42 and 43 are aligned in right angular relationship to the major axis of the bottom wall of the insulating casing 44 of the circuit breaker 4-0 as contrasted to the contact means 37 of the larger modular size circuit breaker shown in FIG- URE 4 which are in general alignment with the major axis of the bottom wall of the insulating casing 36' of the larger circuit breaker 36.

The contact means of the smaller modular size circuit breaker 4%) are therefore disposed as to engage the opposite sides of only one of the laterally extending pins such as 31, 32, 33 and 34 of the contact means of the present invention as illustrated in the perspective view of FIGURE 3. The manner of insertion of the smaller modular size circuit breaker, such as that illustrated in FIGURE 5, into electrical and mechanical engagement with the panel board assembly of the present invention is substantially the same as that previously described for the larger modular size circuit breaker. The insulating casing of the circuit breaker 40 is provided with a lug 45 at one end of its bottom wall which is insertable into one of the U-shaped sections 25 or 25 of the flange 23 or 24, respectively of the panel board as illustrated in FIGURES 1 and 2. The circuit breaker is then rotated about that point of insertion until its opposed contact jaws engage one of the laterally extending cylindrical pins of the panel board contact means in the manner generally shown in FIGURE 1.

The co-action of the circuit breakers in electrical and mechanical engagement with the panel board contact means is illustrated in an enlarged scale by FIGURE 6, which is a partial cross-sectional view showing panel board contact means 50' and 51 disposed in spaced relationship with their respective central blades 52 and 53 generally aligned and parallel with each other. The contact members 50 and 51 are separated by a multiple channel form of appropriate insulation having spaced walls 54, 55 and 56. Cylindrically shaped pins 57 and 58 extend laterally from the central blade 53 of the contact member 51, as do the cylindrically shaped pins 59 and 60 which extend laterally from the central blade 52 of the contact member 50. It will be noted that the cylindrically shaped pins are also in general alignment with each other. The panel board contact means 51 is illustrated as being in mechanical and electrical connection and engagement with a circuit breaker of the larger modular size by means of the opposed contact jaws '61 and 62 engaging the central blade 53 of the panel board contact means 51. As was previously explained in connection with the illustrations of FIGURES 1 and 2, the opposed contact jaws of the larger modular size circuit breaker have a rear portion which is inclined so that it will abut upon the adjacent laterally extending cylindrical pins 57 and 58.

The panel board contact means 50 'as illustrated in FIGURE 6 has two circuit breakers of thesmaller modular size in engagement with it by reason of the two pairs of resilient, opposed contact jaws 63 and 64 being in engagement with the laterally extending cylindrical pins 59 and 60, respectively. As may be seen most clearlyin FIGURE 5, the opposed resilient contact jaws of the smaller modular size circuit breaker are configured so as to have portions which are cylindrically or barrel-shaped so that upon engagement with the laterally extending cylindrical pins of a panel board contact member, the circuit breaker is secured in firm mechanical retention as well as electrical contact. a

FIGURE 7 is an illustration of a two pole circuit breaker assembly comprising two circuit breakers 70 and 71 of the smaller modular size joined by apropriate means such as the rivets shown at 72 and 73. The circuit breakers 70 and 71 are also joined by a common handle tie 74 and their respective contacts 75 and 76 are shown to be engagement with the adjacent transverse members 77 and 78 of two panel board electrical contacts 79 and 80' arranged and disposed in accordance with the concept of the present invention. The contacts 79 and 80lmay be connected to two different bus bars as generally illustrated in FIGURE 1, which bus bars may be in turn supplied by different sources of electrical energy such as two different phases, for instance. Accordingly the adjacent transverse contact members 77 and 78 may each be supplied by a 120-volt source of different phase so as to provide a 240-volt potential therebetween. Thus the circuit breaker assembly of FIGURE 7 may be connected in circuit with major home appliances such as electric ranges which require a 220-240-volt supply. Appropriate insulating means 81 may be interposed as shown in FIGURE 7 between the adjacent contacts 79 and 80, and is particularly desirable when such adjacent contacts are supplied by different sources of electrical energy.

FIGURE 8 illustrates a three pole circuit breaker assembly comprising one circuit breaker 82 of the larger modular size joined with a circuit breaker on either side 83 and 84 of the smaller modular size. It should be noted that although these circuit breakers are of different modular width, they all have side walls of substantially the same outside dimensions and thus may be joined in a unitary-like assembly by appropriate means such as the rivets shown at 85 and 86. Additionally the external handle members of the three circuit breaker units are joined by a common handle tie 87. The three adjacent electrical contacts 88, 89 and 90 may be supplied by different sources of electrical energy such as three different phases, for instance, and accordingly, the inwardly disposed transverse contact members 91 and 92 of electrical contacts 88 and 90, respectively, will be energized by first and second phases of an electrical source, while the central upstanding blade member 93 of the electrical contact 89 will be energized by a third phase of electrical source. Thus the multipole circuit breaker assembly of FIGURE 8 provides a two-times module width, three-pole circuit breaker which affords a wide range of possible combinations of aggregate ampere rating as well as individual ampere ratings of the discrete circuit. breakers connected to each of the three different phases. Appropriate insulating means such as shown at 94 may be positioned and supported between adjacent electrical contacts 88, 89 and as is particularly desirable when such adjacent electrical contacts are connected to different sources of electrical energy.

As will be appreciated by those skilled in the art, the panel board contact means of the present invention and the contact means of the circuit breakers which are positioned and disposed in accordance with modular size, afford a means of segregating any selected or desired portion of a circuit breaker panel board load center so that circuit breakers of the smaller modular size may not be inadvertently or indiscriminately connected in such segregated portion. This preventive action is achieved by eliminating one or more laterally extending cylindrical pins of the panel board contact means in those portions of the panel board where it is not desirable to have the smaller modular size circuit breakers connected. Thus with the cylindrical pins eliminated from a panel board contact member, it may only be engaged by the larger modular size circuit breaker being placed into contact as previously described with the central blade member of the panel board contact means. Though it is usual in panel board installations to include appropriate separating insulating means between adjacent contact member of the panel board, the present invention is so conceived as to prevent the inadvertent connection of a single circuit breaker across two contact members in the absence of such separating insulating means. This feature will be evident to those skilled in the art by reference to FIG- URE 6 where it can be seen that the contact means, such as those shown at 63 or 64 for the smaller modular size circuit breaker, would not be connectable across laterally extending cylindrical pins 58 and 59 even in the absence of the insulating wall 55. Similarly the opposed contact jaws 61 and 62 of the larger modular size circuit breaker is restricted by its configuration and alignment to connect with only a single central blade member of the panel board contact means.

Thus the present invention affords an effective means of segregating portions of the panel board load center so that only a desired size or sizes of modular circuit breakers are connectable in such segregated portion. Moreover, the panel board contact members and the contact members of the circuit breakers configured and disposed in accordance with the concept of the present invention provide a firm mechanical retention when in mutual engagement, as well as a secure and adequate electrical contact. Additionally, both the panel board contact members and the circuit breaker contact means of the present invention are readily and economically fabricated by conventional manufacturing methods without the use of special tooling or materials and provide a strong structure which is long-lasting in service due to a minimum of wear on frictionally engaged parts.

While the invention has been illustrated in only one embodiment, it will be readily apparent that many modifications thereof may be made, and I therefore intend by the appended claims to cover all such modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric circuit control device panelboard comprising a generally planar support, at least two elongated busbars mounted in insulated relation on said support and extending generally parallel thereto and in parallel spaced apart relation to each other, wire connecting means mounted on said busbars respectively for connecting an incoming power conductor thereto, a plurality of contact members supported on said support and electrically connected each to one of said busbars, said control members each having a generally H shaped portion, said H shaped contact portions being in substantial alignment in a row extending generally parallel to said busbars, electric circuit control device retaining means mounted on said support and spaced apart in generally co-planar relation with said aligned contact members whereby electric control devices may be engaged with said retaining means at one end and pivoted about said engagement into electrically plugged in contact with at least a portion of one of said generally H shaped contact portions.

2. An electric circuit controlled device panelboard as set forth in claim 1 wherein said H shaped contact portions are disposed with the leg portions of said H extending generally parallel to said busbars.

3. An electric circuit control device panelboard comprising a generally planar support, at least two elongated electrical busbars supported in insulated relation on said support and extending generally parallel thereto and'parallel to each other, wire connecting means carried by each of said busbars for connecting said busbars to a power conductor, a plurality of contact members supported on said support and electrically connected each to one of said busbars, said contact members each having a generally H shaped contact portion, said contact portions being in substantial alignment in a row extending generally parallel to said busbars, electric circuit control device retaining means mounted on said support in spaced apart relation at each side of said aligned stationary contact members, at least one small-module circuit breaker having one end thereof in engagement with said retaining means, a plug-in type electrical contact carried by said circuit breaker at the end thereof opposite said first end, at least one large-module circuit breaker having the first end thereof in engagement with said retaining means, a plug-in type electrical contact carried by said large-module circuit breaker at the end thereof opposite said first end, said plug-in contact of said small module circuit breaker being in electrical contact with a first portion of one of said H shaped contact members, said plug-in contact of said largeanodule circuit breaker being in electrical contact with a portion of one of said H shaped contact members, the contact surface of said portion of said H shaped contact portion which is engaged by said largemodule circuit breaker extending substantially at rightangles to the portion of said H shaped contact portion which is contacted by said small-module circuit breaker.

4. An electric circuit control device panel board comprising a generally planar base, insulating means mounted on said base, and a plurality of electrical contacts supported on said insulating means, said electrical contacts having central blades extending perpendicularly with respect to said base and in spaced parallel relationship with respect to each other, and at least some of said central blades having a cylindrically shaped pin extending laterally therefrom on each side at right angles and in common alignment.

5. An electric circuit control device panel board comprising a generally planar base, insulating means mounted on said base and a plurality of electrical contacts supported on said insulating means, said electrical contacts having central blades extending perpendicularly with respect to said base and in spaced parallel relationship with respect to each other and at least some of said central blades having two cylindrically-shaped, spaced pins extending from each side at right angles and in parallel alignment.

6. An electric circuit control device panel board comprising a generally planar base, insulating means mounted on said base, a plurality of electrical contacts supported on said insulating means, at least some of said electrical contacts including a central blade member extending generally normal to the plane of said base and at least one cylindrically shaped pin extending laterally from said central blade on each side thereof, and a plurality of circuit breakers of first and second modular size, said circuit breakers of said first modular size including electrical contact means configured and disposed to engage a central blade and said circuit breakers of said second modular size including electricalcontact means configured and disposed to engage one of said cylindrical pins.

7. An electric circuit control device panel board comprising a generally planar base, insulating means mounted on said base, a plurality of electrical contacts supported on said insulating means, at least some of said electrical contacts including a central blade member extending generally normal to the plane of said base and having two cylindrically shaped pins extending laterally from each side of said central blad and in spaced relation to each other, and a plurality of circuit breakers of first and second modular size, said circuit breakers of said first modular size including electrical contact means configured and disposed to engage a central blade and said circuit breakers of said second modular size including electrical contact means configured and disposed to engage one of said lateral cylindrical pins.

8. An electric circuit control device panel board comprising a generally planar base, insulating means mounted on said base, a plurality of electrical contacts, and electrically conductive means connecting and supporting said electrical contacts on said insulating means and being adapted to connect groups of said plurality of said electrical contacts to common sources of electrical energy, at least some of said electrical contacts including a central blade member extending generally normal to the plane of said base and having two cylindrically shaped pins extending laterally from each side of said central blade in spaced relation to each other and generally in alignment with the central axis of said panel board.

9. In a control device panel board, the combination comprising:

(a) a support;

(b) an elongated busbar supported in insulated relationship on said support; and

(c) an electrical contact unit having a contact arm portion electrically connected adjacent one end thereof to said busbar and extending generally normally thereto, said contact arm portion having adjacent its other end a portion with a major dimension in a firs-t direction and a minor in a direction at right angles to said first direction dimension, said contact unit also having a socket-receiving portion projecting from said contact arm portion adjacent said other end thereof generally normally to the plane of said major dimension and extending generally parallel to said busbar, the opposite surfaces of said socket-receiving portion providing a pair of contact surfaces extending generally parallel to said busbar and generally normally to the plane of said major dimension, said socket-receiving portion being adapted to receive a contact socket extending transversely of an associated circuit breaker to provide electrical contact therefor to said busbar.

10. In a control device panel board, the combination comprising:

(a) a support;

(b) two generally parallel elongated busbars supported in insulated relationship on said support; and

(c) an electrical contact unit having a contact arm portion electrically connected adjacent one end thereof to one of said busbars and extending generally normally thereto, said contact arm portion having adjacent its other end a blade portion with its major dimension in a plane extending normally to said support and to said busbars, said contact unit also having a pair of socket-receiving portions projecting to opposite sides of said blade portion adjacent said other end thereof and extending generally parallel to said busbars and normally to said plane of said blade portion, the opposite surfaces of each of said socket-receiving portions providing a pair of contact surfaces extending generally parallel to said busbars and generally normally to said plane, said blade portion being adapted to receive a contact socket extending longitudinally of an associated circuit breaker disposed over said one busbar and each of said socket-receiving portions being adapted to receive a contact socket extending transversely of an associated circuit breaker disposed over the other of said busbars to provide electrical contact therefor to said one busbar.

References Cited by the Examiner UNITED STATES PATENTS Brown 317--119 5 3,095,524 6/1963 Leonard et a1 31712O 3,144,588 8/1964 Platz et a1. 317-119 3,198,992 8/1965 Norden 317-119 3,218,519 11/1965 Casey 317-119 3,271,549 9/1966 Gelzheiser 317-119 10 ROBERT K. SCHAEFER, Primary Examiner.

W. GARVERT, H. O. JONES, Assistant Examiners. 

9. IN A CONTROL DEVICE PANEL BOARD, THE COMBINATION COMPRISING: (A) A SUPPORT; (B) AN ELONGATED BUSBAR SUPPORTED IN INSULATED RELATIONSHIP ON SAID SUPPORT; AND (C) AN ELECTRICAL CONTACT UNIT HAVING A CONTACT ARM PORTION ELECTRICALLY CONNECTED ADJACENT ONE END THEREOF TO SAID BUSBAR AND EXTENDING GENERALLY NORMALLY THERETO, SAID CONTACT ARM PORTION HAVING ADJACENT ITS OTHER END A PORTION WITH A MAJOR DIMENSION IN A FIRST DIRECTION AND A MINOR IN A DIRECTION AT RIGHT ANGLES TO SAID FIRST DIRECTION DIMENSION, SAID CONTACT UNIT ALSO HAVING A SOCKET-RECEIVING PORTION PROJECTING FROM SAID CONTACT ARM PORTION ADJACENT SAID OTHER END THEREOF GENERALLY NORMALLY TO THE PLANE OF SAID MAJOR DIMENSION AND EXTENDING GENERALLY PARALLEL TO SAID BUSBAR, THE OPPOSITE SURFACES OF SAID SOCKET-RECEIVING PORTION PROVIDING A PAIR OF CONTACT SURFACES EXTENDING GENERALLY PARALLEL TO SAID BUSBAR AND GEN- 